/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import java.util.Arrays;
import java.util.Collections;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

import jsinterop.annotations.JsPackage;
import jsinterop.annotations.JsProperty;
import jsinterop.annotations.JsType;

/**
 * Minimal GWT emulation of {@code com.google.common.collect.Platform}.
 *
 * <p><strong>This .java file should never be consumed by javac.</strong>
 *
 * @author Hayward Chan
 */
final class Platform
{
    static <K, V> Map<K, V> newHashMapWithExpectedSize(int expectedSize)
    {
        return Maps.newHashMapWithExpectedSize(expectedSize);
    }

    static <K, V> Map<K, V> newLinkedHashMapWithExpectedSize(int expectedSize)
    {
        return Maps.newLinkedHashMapWithExpectedSize(expectedSize);
    }

    static <E> Set<E> newHashSetWithExpectedSize(int expectedSize)
    {
        return Sets.newHashSetWithExpectedSize(expectedSize);
    }

    static <E> Set<E> newConcurrentHashSet()
    {
        // GWT's ConcurrentHashMap is a wrapper around HashMap, but it rejects null keys, which matches
        // the behaviour of the non-GWT implementation of newConcurrentHashSet().
        // On the other hand HashSet might be better for code size if apps aren't
        // already using Collections.newSetFromMap and ConcurrentHashMap.
        return Collections.newSetFromMap(new ConcurrentHashMap<E, Boolean>());
    }

    static <E> Set<E> newLinkedHashSetWithExpectedSize(int expectedSize)
    {
        return Sets.newLinkedHashSetWithExpectedSize(expectedSize);
    }

    /**
     * Returns the platform preferred map implementation that preserves insertion order when used only
     * for insertions.
     */
    static <K, V> Map<K, V> preservesInsertionOrderOnPutsMap()
    {
        return Maps.newLinkedHashMap();
    }

    /**
     * Returns the platform preferred set implementation that preserves insertion order when used only
     * for insertions.
     */
    static <E> Set<E> preservesInsertionOrderOnAddsSet()
    {
        return Sets.newLinkedHashSet();
    }

    static <T> T[] newArray(T[] reference, int length)
    {
        T[] clone = Arrays.copyOf(reference, 0);
        resizeArray(clone, length);
        return clone;
    }

    private static void resizeArray(Object array, int newSize)
    {
        ((NativeArray) array).setLength(newSize);
    }

    /**
     * Equivalent to Arrays.copyOfRange(source, from, to, arrayOfType.getClass()).
     */
    static <T> T[] copy(Object[] source, int from, int to, T[] arrayOfType)
    {
        T[] result = newArray(arrayOfType, to - from);
        System.arraycopy(source, from, result, 0, to - from);
        return result;
    }

    // TODO(user): Move this logic to a utility class.
    @JsType(isNative = true, name = "Array", namespace = JsPackage.GLOBAL)
    private interface NativeArray
    {
        @JsProperty
        void setLength(int length);
    }

    static MapMaker tryWeakKeys(MapMaker mapMaker)
    {
        return mapMaker;
    }

    static int reduceIterationsIfGwt(int iterations)
    {
        return iterations / 10;
    }

    static int reduceExponentIfGwt(int exponent)
    {
        return exponent / 2;
    }

    /*
     * We will eventually disable GWT-RPC on the server side, but we'll leave it nominally enabled on
     * the client side. There's little practical difference: If it's disabled on the server, it won't
     * work. It's just a matter of how quickly it fails. I'm not sure if failing on the client would
     * be better or not, but it's harder: GWT's System.getProperty reads from a different property
     * list than Java's, so anyone who needs to reenable GWT-RPC in an emergency would have to figure
     * out how to set both properties. It's easier to have to set only one, and it might as well be
     * the Java property, since Guava already reads another Java property.
     */
    static void checkGwtRpcEnabled()
    {
    }

    private Platform()
    {
    }
}
